3.2 Speculative bubbles and low inflation
The emergence of speculative bubbles and a drop in inflation (perhaps into
a deflation), are yet two other market mechanisms to bridge the asset gap.
For reasons similar to those discussed in the emerging markets section,
in a world with substantial asset shortages speculative bubbles are not only
likely to arise, but also provide an important service to those seeking to
store value. In fact, in Caballero et al (2006a), we show that under certain
conditions, bubbles must exist.3 That is, in the absence of a speculative
bubble, there is an excess demand for financial assets and a corresponding
excess supply of goods (see the appendix).
The conditions for the must-have-bubbles result are natural within an
environment in which assets are in short supply. All that is needed is that
the rents accruing to assets currently traded are expected to decline over
time relative to the size of the economy (but not too fast).4 For example, it seems sensible to expect that rents from currently owned land are not likely
to keep up with the economy’s rate of growth for the indefinite future. Note
that these are conditions for fully rational bubbles to exist. It is not that
I beleive that speculative bubbles are always of this nature. The point is
that if the world is in a situation where even fully rational bubbles could be
justified (or nearly so), we should not be at all surprised that speculative
bubbles (rational or not) take hold so easily.
In reality, agents’ portfolios also contain nominal assets issued by the government.
This addition gives the economy another adjustment mechanism,
since a change in the price level affects the real value of these assets. On the
face of an asset shortage, a drop in inflation or an outright deflation when the
shortage is due to a crash in asset values, is a market mechanism to revalue
nominal assets and help covering the asset-gap.